#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
    int A = 0;
    int B = 0;
    int C = 0;
    scanf("%d %d %d", &A, &B, &C);
    int mid = 0, max = 0;
    if (A == B)
        printf("C\n");
    else if (A == C)
        printf("B\n");
    else if (B == C)
        printf("A\n");
    return 0;
}